The invention relates to an explosive powder charge operated setting tool suitable for setting bolts.
European Patent No. 0,346,275 discloses a setting tool, the driving piston of which is braked, as it moves forward, by a ball brake which does not, however, adversely affect the return of the driving piston into its starting position. A recess which is open radially towards the driving piston is provided for this purpose, the axial extent of said recess, with respect to the piston axis, exceeding the diameter of the brake ball and being acted upon by a spring ring which acts radially towards the driving piston, and on its inner circumference has a supporting surface for the brake ball, which is inclined at an acute angle opening towards the driving-in direction, with the result that the brake ball tensions the spring ring as the driving piston moves forward and is intended to come to rest at that end of the recess which is on the driving-in side, but is not intended to reduce the speed of return of the driving piston. Because a spring ring of this type has to be cut open after having been hardened and tempered, in order to be able to act as a spring ring, it causes problems as the cutting-open procedure means that it does not spread in an easily controllable manner, particularly since it is not of uniform thickness. Even small differences in tolerance have the particular effect that braking forces act on the driving piston even when it is returning. This is disadvantageous, in particular in the case of a repeating bolt-setting tool, for reliably returning the driving piston into its starting position.